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' Quarterly Groundwater Report i Frontier Transportation ' 0600-091 June 20, 2000 Page 3 TPH-g, TPH-m (total petroleum hydrocarbons as motor oil), BTEX, and MTBE using EPA methods 8015 modified for diesel, 8015 modified for gasoline, 8015 modified for motor oil, 8020 for BTEX, and 8260 for MTBE, respectively. Laboratory analysis results for all monitoring episodes are presented in Table 1. Recent analytical reports are included as Appendix B. ' Groundwater collected from all eleven monitoring wells identified no detectable dissolved TPH-d and TPH-m concentrations in ten monitoring wells. Historical groundwater data has identified no significant concentration as dissolved TPH-d and TPH-m above 1,500 4g/L in any well except MW-3 since initially tested in August 1996. Maximum concentrations of dissolved TPH-d and TPH-m were identified in MW-3 as 33,000 µg/L in January 2000. Dissolved TPH-d and TPH-m concentrations were identified in MW-3 exclusively as 6,800 µg/L and 10 mg/L, ' respectively, using EPA method 8015. In addition, laboratory analysis of groundwater samples identified no detectable (<50 ' µg/L) concentrations of dissolved TPH-g in ten of the eleven wells sampled. Groundwater collected from monitoring well MW-3 identified dissolved TPH-g concentrations as 4,100 µg/f- using g/Lusing EPA method 8015 modified. Historical groundwater monitoring results have identified TPH-g concentrations above 1,000 µg/L in MW-1 and MW-3 only. Maximum dissolved TPH-g concentrations were identified in March 1998 as 42,000 pg/L in MW-3, which has attenuated and ' remained under 5,000 pg/L since then. Dissolved TPH-g concentrations in MW-1 have attenuated and remained under 710 pg/L since August 1996. Please see Figure 4, Figure 5, and Figure 6 for recent TPH-d, TPH-m, and TPH-g isoconcentration maps. ' No detectable concentrations of dissolved BTEX were identified in groundwater samples collected from monitoring wells MW-1, MW-2, MW-4, MW-5, MW-6, MW-7, MW-8, MW-9, MW-10, and MW-11 using EPA method 8020. Monitoring well MW-3 exclusively identified total dissolved BTEX at a concentration of 324 pg/L. Total dissolved BTEX concentrations in MW-3 have attenuated by 96% since the maximum was identified as 8,350 pg/L in March 1998 twhen groundwater rose to its shallowest depth recorded (7.V bg). See Figure 7 for the recent BTEX Isoconcentration Map. ' MTBE was identified in groundwater from two monitoring wells only. See Figure 8 for the recent MTBE Isoconcentration Map. Groundwater samples collected from monitoring wells ' MW-3 and MW-9 identified an increase in MTBE concentrations from 90 pg/L to 150 µg/]L and from <5 µg/L to 7.7 µg/L, respectively, since the previous monitoring episode (January 2000) using EPA method 8260. However, MTBE concentrations have attenuated from the maximum ' concentrations of 29,400 pg/L in MW-3 and 19 4g/L identified in MW-9. No detectable